It is well known that textiles which have been washed, either in automatic or manual washing processes, and particularly those made of cellulose fibers, present a very unpleasant touch after drying. This undesired hardened feel can be overcome by treating the garments after washing in a rinsing bath with conditioning products. These conditioning compositions are generally liquid dispersions of cationic compounds that are delivered into the rinsing bath through a dispenser, in an automatic process, or directly, in a manual process. Fabric softener (i.e., conditioning) compositions are commonly used to deposit a fabric softening compound onto fabric. Typically, such compositions contain a cationic fabric softening agent dispersed in water. Fabric softener compositions used in the rinse cycle are generally separated into two basic product categories based on solids (active softening agent/fabric softening active) concentration. Compositions containing more than 10% by weight (e.g., 10-50% or 15-25% by weight) solids are often referred to as “concentrated” compositions, and compositions containing less than 10% by weight (e.g., 3-5% by weight) solids are often referred to as “diluted” compositions. Compositions containing softening agent below 5% by weight are sometimes called “ultra dilute,” while softening agent levels in the range of 5-10% by weight are sometimes called “semi-dilute.” Dilute, ultra dilute and semi-dilute fabric softener compositions, each of which are all considered low solids (or low active) compositions, usually have very low viscosity (with minimal or no thickening agents (viscosity control agents)) due to the low active concentration.
Industrial production of liquid softeners, however, demands a high amount of water and expensive packages. The most common and popular rinse-added fabric conditioner products are liquid products. Rinse-added liquid softeners are easy to handle, e.g., easy to dispense and to measure. The liquid form also minimizes the potential for concentrated deposition of the softener on an area of a fabric to cause visible staining. Some automatic clothes washers built with an automatic fabric softener dispenser require the fabric softener in liquid form for proper dispensing.
On the other hand, liquid fabric softener compositions contain a high level of water. The traditional liquid fabric softener products normally contain about 90% to about 95% of water. These products require a great amount of packaging material, the transport of large weight (making shipping expensive), and large shelf space in the retail stores. Recent trends to produce concentrated fabric softeners, with the intention of reducing waste, have improved the environmental impact and decreased the water content in the liquid compositions to about 72% to 80%, which is still a significant amount of water. Parallel with the effort to increase the level of fabric softener active in the liquid composition, another significant improvement in the fabric softener art is the development of rapidly biodegradable fabric softener actives to improve the environmental friendliness of fabric softener products. The new actives consist mainly of cationic quaternary ammonium compounds containing long chain alkyl groups, with at least one ester functional group inserted in some or all of the long chain alkyl groups. Such cationic quaternary ammonium compounds are disclosed, e.g., in E. P. Appln 409,502, Tandela et al., published Jan. 23, 1991; Jap. Pat. Appln 63-194,316, filed Nov. 21, 1988; Jap. Pat. Appln. 4-333,667, published Nov. 20, 1992; Jap. Laid Open Publication 1,249,129, filed Oct. 4, 1989; U.S. Pat. No. 4,767,547, issued Aug. 30, 1988; U.S. Pat. No. 4,808,321, issued Feb. 28, 1989; E. P. Appln 243,735, published Nov. 4, 1987; and U.S. Pat. No. 5,066,414, issued Nov. 19, 1991, all said patents and patent applications being incorporated herein by reference. Liquid formulations also have the disadvantage that the formulations can become unstable upon long term storage, leading to separation of the ingredients. Liquid formulations can also suffer from extremes of temperature, such as freezing temperatures or extremely warm storage temperatures.
In contrast the benefits of solid compositions include: the compactness of the compositions permit the transport of less weight, making shipping more economical; less packaging is required so that smaller and more readily disposable containers can be used; there is less chance for messy leakage; and less shelf space is required in the retail stores. Solid formulations are also more stable to storage, and extremes of temperature.
Despite the many advantages listed above, it is still a challenge to develop a formulation of a solid softener that has a performance comparable to a liquid softener with the same kind and amount of active content. The first challenge in producing a solid softener is developing a formulation that will not melt, “weep”, or separate during typical storage and transport temperatures. Some softening actives, such as dimethyl distearyl ammonium chloride, are themselves already solids at room temperature, so there is little challenge in formulating them into a non-weeping composition. These solid softening actives are effective at softening, but they are not biodegradable and are not considered environmental friendly. The preferred softening actives are biodegradable, such as triethanolamine diester quats (one example of which is methyl bix(ethyl tallowate)-2-hydroxyethyl ammonium methyl sulfate). These biodegradable actives are typically low melting solids that are semi-solid at room temperature, and are much harder to formulate into a non-weeping product.
U.S. Pat. No. 4,769,159 to Copeland describes a solid cast fabric softening product comprising a softening quaternary ammonium cationic surfactant and a blend of dicarboxylic acids. In this case the softening actives being used, such as dimethyl distearyl ammonium chloride, are themselves already solids at room temperature, so there is little challenge in producing a non-weeping formulation. U.S. Pat. No. 6,110,886 to Scepanski describes a solid cast fabric softening product that comprises cationic surfactant and citric acid, but depends upon fatty amines and fatty amine oxides for softening rather than biodegradable quaternary ammonium compounds.
The second challenge in producing a solid softener is developing a formulation that will have an adequate dispense rate when sprayed with water at the typical dispense temperatures of from 46° C. to 54° C. If the dispense rate is too slow it will not be possible to deliver the required amount of formulation during the normal rinse cycle.
As such there is a need for a method to formulate a solid concentrated fabric softener composition based on biodegradable quaternary ammonium compounds.
Accordingly it is an object herein to provide a solid concentrate fabric softener composition that has an actives content of greater than 20%.
It is yet another object of the invention to provide a solid fabric softener that performs at least as well as traditional liquid compositions.
It is yet another object of the invention to provide a solid fabric softener that will have an adequate dispense rate when sprayed with water of from 40° C. to 60° C.
It is yet another object of the invention to provide a solid fabric softener than dissolves appropriately in the rinse cycle, does not “weep” or separate during typical storage and transport temperatures.
It is yet another object to provide a fabric softening composition that is safe, environmentally friendly and economically feasible.
Other objects, aspects and advantages of this invention will be apparent to one skilled in the art in view of the following disclosure, the drawings, and the appended claims.